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from how Stuff works dot com where smart Happens. I am Marshall Brain with today's question, what makes your knuckles pop? If you've ever laced your fingers together, turns your palms away from you and bent your fingers back, you know what knuckle popping sounds like. Joints produced that crack when bubbles burst in the fluids surrounding the joint. Joints are a meeting point between two separate bones, held together and
in place by connective tissues and ligaments. All of the joints in our bodies are surrounded by synovial fluid, a thick, clear liquid. When you stretch or bend your finger to pop the knuckle, you're causing the bones of the joint to pull apart. As they do this, the connective tissue capsule that surrounds the joint is stretched. By stretching this capsule, you increase its volume, and, as we know from chemistry class, with an increase in volume comes a decrease in pressure.
So as the pressure of the synovial fluid drops, gas is dissolved in the fluid become less soluble, forming bubbles through a process called cavitation. When the joint is stretched far enough, the pressure in the capsule drops so low that these bubbles burst, producing the pop that we associate with knuckle cracking. It takes about five to thirty minutes for the gas to redissolve into the joint fluid. During
this period of time, your knuckles won't crack again. Once the gas is dissolved, cavitation is once again possible, and you can start popping your knuckles again. As for the harms associated with this habit, according to Anatomy and Physiology Instructors Cooperative, only one in depth study regarding the possible
detriments of knuckle popping has been published. This study, done by Raymond Broder and published in the Journal of Manipulative and Physiological Therapeutics, examine three hundred knuckle crackers for evidence of joint damage. The results revealed no apparent connection between joint cracking and arthritis. However, habitual knuckle poppers did show signs of other types of damage, including soft tissue damage to the joint capsule and a decrease in grip strength.
This damage is most likely a result of the rapid, repeated stretching of the ligaments around the joint. On the positive side, there's evidence of increased mobility and joints right after popping. When joints are manipulated, the gold g tendon organs, a set of nerve endings involved in humans motions, sense are stimulated and the muscles surrounding the join to relax. This is part of the reason why people can feel loose and invigorated after leaving a chiropractor's office where a
cavitation is induced as part of the treatment. Backs, knees, elbows, and all other movable joints are subject to the same kind of manipulation as knuckles are. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff Works dot com. For more on this and thousands of other topics. Go to how stuff works dot com and be sure to check out the brain stuff blog on the how stuff
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